Saturday, April 12, 2014

Book review: “The Theoretical Minimum – Quantum Mechanics” By Susskind and Friedman

Quantum Mechanics: The Theoretical Minimum
What You Need to Know to Start Doing Physics
By Leonard Susskind, Art Friedman
Basic Books (February 25, 2014)

This book is the second volume in a series that we can expect to be continued. The first part covered Classical Mechanics. You can read my review here.

The volume on quantum mechanics seems to have come into being much like the first, Leonard Susskind teamed up with Art Friedman, a data consultant whose role I envision being to say “Wait, wait, wait” whenever the professor’s pace gets too fast. The result is an introduction to quantum mechanics like I haven’t seen before.

The ‘Theoretical Minimum’ focuses, as its name promises, on the absolute minimum and aims at being accessible with no previous knowledge other than the first volume. The necessary math is provided along the way in separate interludes that can be skipped. The book begins with explaining state vectors and operators, the bra-ket notation, then moves on to measurements, entanglement and time-evolution. It uses the concrete example of spin-states and works its way up to Bell’s theorem, which however isn’t explicitly derived, just captured verbally. However, everybody who has made it through Susskind’s book should be able to then understand Bell’s theorem. It is only in the last chapters that the general wave-function for particles and the Schrödinger equation make an appearance. The uncertainty principle is derived and path integrals are very briefly introduced. The book ends with a discussion of the harmonic oscillator, clearly building up towards quantum field theory there.

I find the approach to quantum mechanics in this book valuable for several reasons. First, it gives a prominent role to entanglement and density matrices, pure and mixed states, Alice and Bob and traces over subspaces. The book thus provides you with the ‘minimal’ equipment you need to understand what all the fuzz with quantum optics, quantum computing, and black hole evaporation is about. Second, it doesn’t dismiss philosophical questions about the interpretation of quantum mechanics but also doesn’t give these very prominent space. They are acknowledged, but then it gets back to the physics. Third, the book is very careful in pointing out common misunderstandings or alternative notations, thus preventing much potential confusion.

The decision to go from classical mechanics straight to quantum mechanics has its disadvantages though. Normally the student encounters Electrodynamics and Special Relativity in between, but if you want to read Susskind’s lectures as self-contained introductions, the author now doesn’t have much to work with. This time-ordering problem means that every once in a while a reference to Electrodynamics or Special Relativity is bound to confuse the reader who really doesn’t know anything besides this lecture series.

It also must be said that the book, due to its emphasis on minimalism, will strike some readers as entirely disconnected from history and experiment. Not even the double-slit, the ultraviolet catastrophe, the hydrogen atom or the photoelectric effect made it into the book. This might not be for everybody. Again however, if you’ve made it through the book you are then in a good position to read up on these topics elsewhere. My only real complaint is that Ehrenfest’s name doesn’t appear together with his theorem.

The book isn’t written like your typical textbook. It has fairly long passages that offer a lot of explanation around the equations, and the chapters are introduced with brief dialogues between fictitious characters. I don’t find these dialogues particularly witty, but at least the humor isn’t as nauseating as that in Goldberg’s book.

All together, the “Theoretical Minimum” achieves what it promises. If you want to make the step from popular science literature to textbooks and the general scientific literature, then this book series is a must-read. If you can’t make your way through abstract mathematical discussions and prefer a close connection to example and history, you might however find it hard to get through this book.

I am certainly looking forward to the next volume.

(Disclaimer: Free review copy.)


  1. Physics' mathematics is rich, wide, and deep. There are legitimate not-closed forms (pendulum equation). Corrections need not be valid: Euclid, cartography, then Bolyai. Relativity and QM cannot be reconciled. An defective postulate must be externally challenged. Relativity is empirically perfect without excuses. Recipes for its failure (Ashtekar plus Immirzi; ECKS gravitation) require testing ingredients default denied by physics. Quantum gravitation, SUSY, and dark matter are forever- yet never-corrected tests of faith.

  2. 0. O.k.
    Trade ya my 2 Volumes Musimathics by Loy for ya Volumes by Susskind and Friedman!

    No way! patient!

    "That having been said, I'm not a teenager anymore and frankly don't have much use for the book. Which is why I'll give away my copy for free. The book will go to the first person who has a mailing address in Europe and leaves a comment to this blogpost telling us why you want the book and what is your interest in physics. - Bee

    Update: The book is gone.

    You know we will be writing our own books after everyone has had their say.

    We'll point out where everyone else when astray and praise the heroics anyway. The beauty of hindsight... (and slow reading).

    The best part is the part where we will have the last word - because we all know at a later age, none can repeat their performance from the brilliance of their past performance.

    Unless of course the theoretical is reduced to a minimum.

  3. My string friend did not make tenure so left academia. But during our discussions he remarked that he envied my time for reading. A clever remark at the time was that by the time one completes an undergraduate course what is learned in that time is already obsolete.
    The philosophy of physics is the philosophy of nature but originally the word also meant growth much in the complexity of foundations (of the minimum for theoretical inquiry the addressing and attempt to resolve these ancient meanings.)
    Is a book such as this helpful as a bridge to deeper wisdom although Pythagoras prefered to be called a lover of wisdom?
    Physics in the context of its time can be a most interesting and educational history. It takes strength and sacrifice to pursue such noble calling and there is no guarentee the wiser souls survive. I wonder have so many kept faith when their world worked chaos like war or plague around them.
    Theory must be valuable as well as developed technology that even in the world war conquest of another states colonies was a windfall for national advancement dominated by the West.
    Perhaps we need to fall back to a few mathematically sound regions of naturalism. Global sharing the wisdom is presently untenable, illogical.
    I wrote a large book at the time also which the bureaucracy said fulfilled my work requirement while an at home father. Only to be dismissed by veto and shortly so despite the effort.
    Yet a society is at risk to fire its bureaucrats or its intellectuals radically.
    Does it take a Carl Sagan to popularize physics that research get minimum growth and funding?
    I like to think there is some truth to the idea (I did not notice who first said it) that the time paradoxes are solved in a multiverse because somewhere there has to be an original Shakespeare. That lonely sense of the creative where perhaps we are our most authentic self in the best path.
    What is the minimum, and most all are capable, to learn to recognize originality in a subject and that the value of our projects can be understood? Are we ever free from local or global stumbling into dead ends.
    Each parent thinks to write this era's new children's books while older ones were as good as if some conserved wisdom fell into the black hole of our hearts then pointlessly rearranged from that mangled.
    Some days I am a decade ahead and other days catching up from behind.
    May all your chocolate bunnies not be hollow.

  4. I saw this book recently in a bookshop. Does it offer anything to someone who does know at least the basics of quantum mechanics?

    Some typos:

    "The result is an introduction to quantum mechanics like I haven’t seen one before" should be "The result is an introduction to quantum mechanics like I haven’t seen before."


    "the hydrogen atom or and the photoelectric effect" should be "the hydrogen atom or the photoelectric effect".

  5. Bee - It sounds like he will be taking all of his lecture series (available on youtube) and converting to text. Not a bad thing.

  6. Phillip: Thanks for pointing out the mistakes, I have corrected these. Best,



COMMENTS ON THIS BLOG ARE PERMANENTLY CLOSED. You can join the discussion on Patreon.

Note: Only a member of this blog may post a comment.